BACKGROUND: Inositol has been reported to improve insulin sensitivity since it works as a second messenger achieving insulin-like effects on metabolic enzymes. The aim of this study was to evaluate the inositol and alpha lipoic acid combination effectiveness on metabolic syndrome features in postmenopausal women at risk of breast cancer.

METHODS: A six-month prospective, randomized placebo-controlled trial was carried out on a total of 155 postmenopausal women affected by metabolic syndrome at risk of breast cancer, the INOSIDEX trial. All women were asked to follow a low-calorie diet and were assigned randomly to daily consumption of a combination of inositol and alpha lipoic acid (77 pts) or placebo (78 pts) for six months. Primary outcomes we wanted to achieve were both reduction of more than 20% of the HOMA-IR index and of triglycerides serum levels. Secondary outcomes expected were both the improvement of high-density lipoprotein cholesterol levels and the reduction of anthropometric features such as body mass index and waist-hip ratio.

RESULTS:: A significant HOMA-IR reduction of more than 20% was evidenced in 66.7% (P <0.0001) of patients, associated with a serum insulin level decrease in 89.3% (P <0.0000). A decrease in triglycerides was evidenced in 43.2% of patients consuming the supplement (P <0.0001). An increase in HDL cholesterol (48.6%) was found in the group consuming inositol with respect to the placebo group. A reduction in waist circumference and waist-hip ratio was found in the treated group with respect to the placebo group.

CONCLUSIONS:: Inositol combined with alpha lipoic acid can be used as a dietary supplement in insulin-resistant patients in order to increase their insulin sensitiveness. Daily consumption of inositol combined with alpha lipoic acid has a significant bearing on metabolic syndrome. As metabolic syndrome is considered a modifiable risk factor of breast tumorigenesis, further studies are required to assess whether inositol combined with alpha lipoic acid can be administered as a dietary supplement in breast cancer primary prevention